Here is the full list of all 50 Injustice: Gods Among Us achievements worth 1,000 gamerscore.
Win with Batman using every special move and his Supermove
Reach Level 100
Unlock everything in Archives
Unlock all costumes in the Archives
Complete 100% of Story Mode
Win all story mode minigames
Complete 50% of Story Mode
Play 200 complete Online Matches
Win 100 complete Online Matches
Dethrone the King in an online match
Defeat a Survivor
Enter Online Practice with someone on your friends list
Win 10 complete Ranked matches
Win a single online match
Win 1 complete Ranked match
Perform a 10 hit combo with every character
Complete Classic Battle with all characters
Perform every character's supermove
Knock opponent through all transitions across all levels
Cause maximum damage in all Arenas (does not include Practice mode)
Win a Clash sequence with any character
Complete Classic Battle with any character
Complete 1 S.T.A.R. Lab Mission
Get 3 stars on 1 S.T.A.R. Lab Mission
Send an opponent through all three Metropolis transitions in one fight
Unlock a costume in the Archives
Defeat every Villain With Batman
Reach Level 10
Knock an opponent through a transition
Equip a new Background Image
Equip a new Icon
Win a match with the super move of any character
Make a comeback when at low health (10% or less)
Perform 8 throws and win in a multiplayer match
Use every interactable and win in a multiplayer match
Win a match as Deathstroke without missing a shot (minimum 12 shots)
Win a multiplayer match with a timeout
Win a match with Green Arrow using only arrows
Vote Correctly in a KOTH match
View Your Hero Card
Equip a new Character Portrait
Enter Practice Mode
Complete Tutorial
Complete Battle Mode
Beat All S.T.A.R. Lab Missions (Excluding DLC)
Get 100 Stars in S.T.A.R. Lab Mode
Complete All S.T.A.R. Lab Missions with 3 Stars
Perform every special move of every character
Perform every Meter Burn special move of every character
Perform every level interaction once